That said, as far as you are concerned (legally) these are NOT "inherited guns" unless your uncle specifically named you in the will as the recipient of these firearms. It sounds like your father inherited them, and as the heir HE could legally bring them from AZ to WA without any transfer paperwork -- even if this was after the 1968 Gun Control Act.

Once your father had them in WA (assuming he is also a WA resident), anything that transpired between your father and you would have been subject only to whatever WA state law was at the time.